There is increasing recognition that apoptotic cell death is a key factor restraining tumor development, and that dysfunctional apoptosis is a common feature of cancer cells leading to therapeutic failure. This is particularly true for melanoma, which is usually resistant to radiation and chemotherapeutic drugs that eliminate cells through induction of apoptosis. Thus, understanding the molecular basis for this apoptosis resistance has tremendous clinical relevance. The long-term goals of this project are to understand how apoptosis is regulated in melanocytic cells, and how dysregulation of this process may lead to mel'anoma and confer resistance to therapy. Previously, we found that an inhibitor of apoptosis termed Survivin is expressed in melanoma but not in normal melanocytes, and that blocking Survivin triggers spontaneous apoptosis in melanoma cells. Our hypothesis, based on these and additional preliminary observations, is that Survivin expression contributes to the progression from normal melanocyte to melanoma and may represent an important viability factor for melanoma cells. Three specific aims are proposed. 1) To study the consequences of Survivin expression in melanocytes. We will use both adenoviral and transgenic-based approaches to define the role of Survivin expression in melanocyte transformation. 2) To examine biochemical events resulting from Survivin inhibition in melanoma. We will use cell lines expressing inducible Survivin mutants to investigate caspase-dependent and mitochondrial events leading to apoptosis upon Survivin targeting. 3) To investigate the regulation of caspase-independent apoptotic events associated with Survivin inhibition. These experiments will focus on the roles of mitochondrial apoptosis-inducing factor and cleavage of a Survivin-like molecule (Livin) in melanocytes and melanoma cells. In summary, these proposed studies promise to elucidate mechanisms of apoptosis regulation in normal and malignant melanocytes, and may identify new molecular approaches for therapeutic intervention in cancer. [unreadable] [unreadable]